How Big is the Moon? - Lesson for Kids

Instructor: Wendy McDougal

Wendy has taught high school Biology and has a master's degree in education.

When you look into the sky, you often see our one-and-only natural satellite: the moon. Sometimes appearing huge, and sometimes tiny and distant, our lunar friend always seems to be changing. How big is the moon? Read more to find out.

An Ever-Changing Celestial Body

When was the last time you saw a full moon? It might have seemed so huge you felt like you could reach out and touch it. Contrast this with a distant glimmering crescent moon that appears to be far-off in the night sky. One thing is for certain: the shape and size of the moon appears to change constantly. But the actual size of the moon is always the same. How big (or small) is the moon? In this lesson, we will uncover the true size of Earth's constantly orbiting satellite.

A full moon can appear to be enormous
Moon over mountains

The Moon Compared to the Earth

For starters, is the moon bigger or smaller than Earth? The answer is: smaller. Moons are always smaller than the planets that they orbit. To better visualize the comparison of Earth with the moon, imagine a tennis ball (the moon) next to a basketball (Earth). Now, that's not to say the moon is smaller than all of the planets in our solar system. Our moon is actually larger than dwarf planet Pluto!

A comparison of the moon next to Earth
Moon and Earth comparison

Let's take a look at some actual statistics about the size of the moon. The measurement around the widest part of the moon, or its equator, is almost 11,000 km or 6,780 miles. In mathematical terms, this is the moon's circumference. If you were to drive continuously around the moon at 60 mph, the trip would only take you about 113 hours total! Not bad for a full lunar road trip.

In comparison, to give you some perspective, let's look at the size of our Earth. At the equator, the circumference of Earth is about 40,000 km, or just under 25,000 miles. Quite a bit larger than the moon, wouldn't you say? Driving non-stop around Earth (which is quite impossible, yes) at 60 mph, the trip would take about 416 hours. We can see that at the equator, Earth is about four times the size of the moon. But the difference in volume, or amount of space inside each sphere, is much greater. You could fit fifty moons inside Earth!

How do You Measure the Moon?

How do we know the exact size of celestial bodies like moons and planets? Of course, we can use tools like rulers and a measuring tape to assess things like shoe size, room dimensions, and a person's height. However, how does one possibly measure something like Earth or moon? The answer can be found in math!

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